Chapter 2

Question 1

Atom

Answer 1

A subatomic particle that constitutes the fundamental building block of ordinary matter; the smallest identifiable unit of an element.

Question 2

Law of conservation of mass

Answer 2

In a chemical reaction, matter is neither created nor destroyed

Question 3

Law of definite proportions

Answer 3

All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.
E.g. H2O
16 g 0/2gH = 8:1

Question 4

Law of multiple proportions

Answer 4

When two elements form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers. E.g. Mass oxygen to 1 g carbon in carbon dioxide/mass oxygen to 1 g carbon in carbon monoxide

Question 5

John Dalton’s atomic Thoery

Answer 5

1) Each element is composed of tiny, indestructible particles called atoms (FALSE:CAN BE DESTROYED VIA NUCLEAR REACTIONS.
2) All atoms of a given element has the same mass and other properties that distinguish them from the atoms of other elements (FALSE: ISOTOPES)
3) Atoms combine in simple, whole number ratios to form compounds (TRUE)
4) Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms only change the way they are bound together with atoms (FALSE- NUCLEAR REACTIONS)

Question 6

J.J. Thompson’s Cathode Ray

Answer 6

Discovery of Electron
Thompson applied a high electrical voltage bw two electrodes at either end of a cathode ray tube.

Beam of particles (cathod rays) traveled from the negatively charged electrode (CATHODE) to the positively charged electrode (ANODE)

Particles travel in straight lines, are independent of the composition of the material from which they originate, and they carry a negative electrical charge. Electrostatic forces, electrical field

Charge to mass ratio of the electron: 1g/ -1.76x10^8 C

Question 7

Millikan’s Oil Drop Experiment

Answer 7

Charge of the electron.

Sprayed oil into fine droplets. Droplets fell through small hole in lower portion of apparatus. Drops aquired electrons that had been produced by ionizing radiation. Electrons imparted a negative charge to the drops. Positive changed plate on top, negatively charged plate on bottom. He could slow or even reverse the free fall of negatively charged drops (like charges repel each other)

Charge of single electron: -1.60x10^-19

Question 8

Ernest Rutherford’s gold-foil experiment

Answer 8

Small, dense nucleus. Atom is mostly empty space.

Plum pudding model

Base of nuclear theory:

• Most of mass is positive charge contained in small core (nucleus)
• Most of volume of atom is empty space, with tiny negatively charged electrons are dispersed
• As many negatively charged electrons outside the nucleus as there are positively charged particles (protons) within the nucleus, so atom is electrically neutral)

Question 9

James Chadwick’s discovery of the neutron.

Answer 9

Previously unaccounted for mass of atom is due to neutrons. Mass is similar to proton, but has no electrical charge.

Question 10

Subatomic Particles
Proton
Neutron
Electron

Answer 10

Mass, Charge, Charge (C)
P:1.00727 amu, +1, +1.60218x10^-19
N: 1.00866 amu, 0, 0
E: .00055 amu, -1, -1.60218 x10^-19

Question 11

Isotopes

Answer 11

Atoms of the same element with the same number of protons but different number of neutrons and different masses.

Most elements have at least two naturally occuring isotopes.

Question 12

Periodic Table

Answer 12

Introduced by Mendeleev. Elements arranged in order of increasing atomic number and arranged with similar properties fall in same vertical groups.

Columns= groups/families 1A-8A (representative/main elements)
1A: Alkali metals
2A: Alkaline earth metals
7A: Halogens
8A: Noble Gases

Rows=periods

Question 13

Metals

Answer 13

Good conductors of heat & electricity. Can be pounded into flat sheets (malleable), wires. Shiny. Lose electrons when they undergo chemical changes

Question 14

Non-metals

Answer 14

Varied properties (gases, liquids, solids) Poor conductors of heat/electricity. Tend to gain electrons under chemical changes.

Question 15

Metalloids

Answer 15

Mixed properties. Some classified as semi conductors- intermediate electrical conductivity (highly temperature dependent). We are able to change and control the conductivity of semiconductors and they are useful in manufacturing of electronic chips and circuits.

Question 16

Ions

Answer 16

Formed by transfer of electrons from one atom to another atom (or group of atoms - METAL TO NON METAL

Typical charges by group:
1A: 1+
2A: 2+
7A: 1-
Noble gases: no charge
Transition elements=several charges

Question 17

Cations

Answer 17

Positively changed. Typically formed from metals that lose electrons

Question 18

Anions

Answer 18

Negatively changed and typically formed from non metals that gain electrons

Question 19

Atomic mass unit

Answer 19

AMU

1/12 the mass of a carbon atom containing six protons and six neutrons. 1 atom of 12C weighs exactly 12 amu

Question 20

Mass spectrometer

Answer 20

Separates particles according to their mass. Sample is injected into the instrument and vaporized. Vaporized atoms are ionized by an electron beam. Electrons in beam collide with atoms, removing electrons and creating positively charged ions. Ions are accelerated into magnetic field. When ions drift thru magnetic field, force bends their trajectory. Amount of bending depends on mass of the ions. Trajectories of lighter ions are bent more than those of heavier ones.

Determines atomic mass of sample of the element.

Question 21

Mole

Answer 21

Chemist’s dozen. The amount of material containing 6.022x10^23 particles. Avogadro’s number.
Relationship between mass and number of atoms.

Question 22

Atomic mass vs molar mass

Answer 22

Atomic mass: total number of protons and neutrons

Molar mass: grams per mole